This invention relates to a mechanism for providing tension, that is, a mechanism wherein a pushing force continuously acts in a first direction and, when a reaction force acts, the mechanism displays nearly properties of rigid body. Such kind of mechanism is used in such a case when a chain or a belt is pressed with a force having a fixed direction, for instance, in chain tensioner, belt tensioner or the like, and in case wherein characteristics of the rigid body are required when a reaction force against said fixed direction acts on said tensioner. In other words, the chain tensioner is used to provide a fixed tension to a chain by pressing said chain in the fixed direction when said chain occurs the slackness by elongation or wear of the chain during the use. In this case, the characteristics of nearly the rigid body are desirable for the reaction force against said pressing direction.
Heretofore, for instance, in case of the chain tensioner, the readjustment thereof is performed with man-power according to the elongation of the chain or automatically. The former, however, is comparatively cheap, but difficult in maintenance and has such defects as noise due to the reason that the former becomes a perfect rigid body in the direction of the reaction force and the intense wear of the tensioner unendurable to the use for long period of time etc. On the other hand, the latter is complicated in whole mechanism and high cost since the oil pressure or the like is used.